351W Stroker Kits: 393 vs 408 vs 427 Windsor
For most 351 Windsor builds, the 408 is the pick. It's a 4.030 in bore with a 4.000 in stroke, and it's the 351W stroker we list. The 393 uses a shorter 3.850 in stroke. It's the milder, lower-stress option. We don't list a 393W kit today, so call us if that's the way you want to go. The 427 kit we list, Scat 1-46580BI, is 4.125 in bore × 4.000 in stroke with 6.250 in H-beam rods and a forged crank. It needs an aftermarket 9.500 in deck block with 2.750 in Cleveland-size mains and a 4.125 in bore. It will not fit a stock 351W (3.000 in mains). Every stroker kit includes the crank, rods, pistons, rings and bearings.
Key takeaways
- The 408 is the 351W stroker we get asked about most. We list two: Eagle 14129030 (forged crank, forged pistons, 6.250 in H-beam rods) and Scat 1-94306 (cast crank, forged pistons, 6.200 in I-beam rods). Both are 351W 408 kits with 3.000 in mains.
- The 427 kit we list, Scat 1-46580BI, is 4.125 in bore × 4.000 in stroke with 6.250 in H-beam rods and a forged crank. It needs an aftermarket 9.500 in deck block with 2.750 in Cleveland-size mains and a 4.125 in bore. It will not fit a stock 351W (3.000 in mains).
- Blocks that fit that 427 kit: the Ford Performance BOSS 351 9.5 in deck block, and Dart and World 351-family blocks with Cleveland-size mains. Dart and World make more than one casting, so confirm yours has 2.750 in mains before you order.
- Bigger isn't automatically better. On a sound stock 351W block, the 408 is the safer street choice.
- Stock 351W deck height is 9.500 in on 1971-and-up blocks. 1969–70 blocks are 9.480 in. That 0.020 in difference changes piston compression height and deck clearance, so measure the deck before you buy pistons or a kit.
- A roller-cam or flat-tappet 351W block does not change which of these rotating kits you order. A 4.000 in stroke still needs block and cam clearancing — the bottom of the bores, and rod-to-cam — before final assembly. Tell us which cam you have. Don't assume a large-base-circle roller cam will clear.
How to choose your 351W stroker kit
- Check your block. Is it a factory 351 Windsor or an aftermarket block? Have the walls sonic-checked before a 4.030 in bore. Measure the deck: 9.500 in on 1971-and-up blocks, 9.480 in on 1969–70 blocks. That 0.020 in changes piston compression height and deck clearance.
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Pick displacement by use.
- 393: a mild, lower-stress street engine (3.850 in stroke on a 351W). We don't list a 393W kit today.
- 408: the all-round street and strip stroker on a standard 351W block.
- 427: the most displacement with the kit we list. It needs an aftermarket 9.500 in deck block with 2.750 in Cleveland-size mains and a 4.125 in bore, such as a Ford Performance BOSS 351, or a Dart or World block with Cleveland-size mains. It will not fit a stock 351W (3.000 in mains).
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Pick the crank and rods for the job.
- Cast crank with I-beam rods, for street use: Scat 1-94306.
- Forged crank with H-beam rods, for higher stress or a power adder: Eagle 14129030 and Scat 1-46580BI.
- We don't quote horsepower limits. Call us with your goal.
- Match the balance. These three kits are internal-balance designs. Use a matching internal or neutral damper and flexplate or flywheel; a stock externally balanced 351W damper or flexplate will not match. Scat 1-46580BI is internally balanced by Scat. Eagle 14129030 and Scat 1-94306 ship unbalanced and must be balanced before they go in. None of the three includes a damper or a flexplate or flywheel.
- Plan the rest of the short block. Clearancing, ring and bearing clearance, and machine work all come after the block is measured. Then call 310-784-1010 or email sales@coasthigh.com before you order. Tell us your block, your goal, and which cam you have.
393 vs 408 vs 427 compared
| 351W (stock, for reference) | 393W | 408W | 427W (as listed) | |
|---|---|---|---|---|
| Bore | 4.000 in | 4.030 in | 4.030 in | 4.125 in |
| Stroke | 3.500 in | 3.850 in | 4.000 in | 4.000 in |
| Calculated displacement | 351.9 ci | 392.9 ci | 408.2 ci | 427.7 ci |
| Rods in kits we list | n/a | n/a (no 393W kit listed) | 6.250 in H-beam (Eagle 14129030) / 6.200 in I-beam (Scat 1-94306) | 6.250 in H-beam (Scat 1-46580BI) |
| Crank in kits we list | n/a | n/a | Forged (Eagle 14129030) / Cast (Scat 1-94306) | Forged (Scat 1-46580BI) |
| Pistons in kits we list | n/a | n/a | Forged (both kits) | Forged |
| Mains | 3.000 in | 3.000 in | 3.000 in | 2.750 in Cleveland-size |
| Balance | n/a | n/a | Internal-balance design. Both kits ship unbalanced and must be balanced before they go in. Damper and flexplate or flywheel not included. | Internal. Scat 1-46580BI is internally balanced by Scat. Damper and flexplate or flywheel not included. |
| Block | Factory 351W (deck 9.500 in on 1971-and-up; 9.480 in on 1969–70 — measure it) | 351W | 351W (3.000 in mains) | Aftermarket 9.500 in deck block with 2.750 in Cleveland-size mains and a 4.125 in bore, such as a Ford Performance BOSS 351, or a Dart or World block with Cleveland-size mains. Will not fit a stock 351W (3.000 in mains). |
| Listed at Coast High | n/a | Not listed | 2 kits | 1 kit |
Some 427W kits on the market use a 4.170 in stroke on a 4.030 in bore (about 425.5 ci). We don't list one, so it's not in the table.
Shop the 351W kits: Ford 351W engine kits.
Frequently asked questions
Which 351W stroker kit should I buy, 393, 408 or 427?
For most street and strip 351W builds, the 408 (4.030 in bore, 4.000 in stroke) is the common choice. Choose the 393 for a milder, lower-stress build, and the 427 only with a block that supports it.
Will a 408 stroker kit fit my stock 351 Windsor block?
The 408 kits we list are made for 351 Windsor blocks with 3.000 in mains and a 4.030 in bore. Have the block sonic-checked and measured for deck height first, and expect block and cam clearancing (the bottom of the bores, and rod-to-cam). Tell us your block and which cam you have before you order.
Do I need an aftermarket block for a 427 Windsor?
The 427 kit we list uses a 4.125 in bore, 9.500 in deck and 2.750 in Cleveland-size mains. A stock 351W block can't safely be bored to 4.125 in and has 3.000 in mains, so plan on an aftermarket block that matches those specs. Examples are the Ford Performance BOSS 351 9.5 in deck block, and Dart and World 351-family blocks with Cleveland-size mains. Confirm your casting has 2.750 in mains before you order.
What comes in a stroker kit?
Every stroker kit includes the crank, rods, pistons, rings and bearings.
Cast or forged crank for a 408?
Our listings offer both: cast crank with I-beam rods (Scat 1-94306) and forged crank with H-beam rods (Eagle 14129030). Tell us your power goal and use when you call 310-784-1010.
Is a 393 stroker worth it over a 408?
The 393's shorter 3.850 in stroke is gentler on the block and rods. Most builders who can fit a 408 choose it for the extra displacement. We don't list a 393W kit today, so call to ask about options.
Tell us your block and goal
Don't guess on fitment. Email sales@coasthigh.com or call 310-784-1010 or 310-784-2977.
Starting from a 302 / 5.0 block instead of a 351W? Shop Ford 302 stroker kits (331, 347 and 363; the 363 needs an aftermarket 4.125 in bore block).